A low vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel

Abstract

A kind of low vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel, the present application belongs to laser welding technical field.The present application solves the problem that the existing welding method cannot realize the low-cost and high-quality connection of medium thickness and above GH4169 alloy and SS304 stainless steel.One, welding assembly;Two, low vacuum laser welding;Three, heat treatment.The present application is used for the low vacuum laser welding of GH4169 high-temperature alloy and SS304 stainless steel.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology. Background Technology

[0002] In the aerospace field, hot-end components, such as thrust chambers, endure high-temperature, high-pressure, and high-speed gas flows and the resulting vibrations and impacts during service. These harsh conditions place stringent demands on material properties and welding techniques. Using a single material is insufficient to meet product quality requirements. Therefore, different materials are used in different parts of the thrust chamber based on specific service conditions. This not only fully utilizes the superior properties of various materials but also reduces the consumption of rare and precious metals, improving economic efficiency. This is a major trend in thrust chamber manufacturing. GH4169 high-temperature alloy is an age-hardening precipitation-strengthened nickel-based high-temperature alloy with advantages such as high operating temperature, strong stress resistance, and strong corrosion resistance, making it the most widely used high-temperature alloy currently. SS304 stainless steel is an 18-8 chromium-nickel austenitic stainless steel with a stable austenitic structure, high strength, good ductility and toughness, low cost, and good high-temperature performance, making it widely used in rocket engines.

[0003] The welding of GH4169 high-temperature alloy and SS304 stainless steel is a typical dissimilar metal welding, which has many problems: (1) High-temperature alloy and austenitic stainless steel have low thermal conductivity and large coefficient of linear expansion, resulting in high welding stress during the welding process and easy to produce welding cracks; (2) High-temperature alloy liquid metal has strong viscosity, and its joint molten pool metal is difficult to wet and spread, resulting in poor weld formation and shallow penetration. Traditional welding methods cannot improve its fluidity even if the welding heat input is increased, but will instead increase the sensitivity of weld cracks; (3) The liquid metal formed by high-temperature alloy and stainless steel has weak fluidity, and the closed gas generated during the welding process is difficult to escape in time, which easily produces welding porosity defects; (4) Due to the segregation of Nb element during solidification, GH4169 high-temperature alloy and SS304 stainless steel dissimilar metal welds are prone to produce a large amount of brittle Laves phase, reducing the joint strength. Furthermore, the generation of the Laves phase is related to the welding heat input. For welding of joints with medium thickness and above, high welding heat input will cause the weld to generate a higher content of brittle Laves phase. (5) SS304 stainless steel lacks solid solution strengthening elements such as Mo and age-hardening elements such as Al and Ti compared to GH4169 high-temperature alloy. This results in a lower strengthening effect of strengthening elements in the weld, which limits the mechanical properties of dissimilar metal joints.

[0004] Based on the aforementioned problems, traditional welding methods are insufficient for welding dissimilar metals such as GH4169 alloy and SS304 stainless steel, resulting in defects such as porosity, cracks, and abundant brittle phase precipitation in the weld. Especially for the joining of medium-thickness or thicker GH4169 alloy and SS304 stainless steel, the only welding method currently available that achieves high forming quality, a large aspect ratio weld, and low brittle phase content is vacuum electron beam welding. However, vacuum electron beam welding technology suffers from high equipment costs, long vacuuming times, and low production efficiency. Furthermore, the weld still exhibits brittle phase precipitation and low strengthening element content, significantly limiting the engineering applications of welding GH4169 alloy and SS304 stainless steel. Therefore, there is currently no welding method or process that can achieve low-cost, high-quality joining of medium-thickness or thicker GH4169 alloy and SS304 stainless steel. Summary of the Invention

[0005] The present invention aims to solve the problem that existing welding methods cannot achieve low-cost and high-quality connection between medium-thickness and thicker GH4169 alloy and SS304 stainless steel, and provides a low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel.

[0006] A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel is performed according to the following steps:

[0007] I. Assembly of welded parts:

[0008] The dissimilar metal base materials to be welded are assembled and then fixed on a two-dimensional moving platform inside the vacuum chamber to form a dissimilar metal sample to be welded.

[0009] The dissimilar metal base materials to be welded are GH4169 high-temperature alloy and SS304 stainless steel;

[0010] II. Low-vacuum laser welding:

[0011] Under the conditions of laser power of 2kW~8kW, welding speed of 0.5mm / min~3.5mm / min, laser spot diameter of 0.4mm~0.6mm, laser beam incident angle of 80°~100°, laser defocusing amount of -3mm~-12mm, and laser beam offset of 0mm~0.6mm, a two-dimensional moving platform is moved, and the laser moves along the welding path to form a weld. After the laser welding is completed, the workpiece is cooled to room temperature and then removed.

[0012] III. Heat Treatment:

[0013] The weldment is subjected to a two-stage aging heat treatment, which completes the low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel.

[0014] The beneficial effects of this invention are:

[0015] (1) The present invention provides a low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel. Through environmental optimization, laser welding is performed in a low-vacuum environment. Without increasing the welding heat input, the welding penetration ability and weld formation quality can be effectively improved, and a high-quality, high-depth-to-width ratio weld can be obtained for the dissimilar metal butt structure of GH4169 high-temperature alloy and SS304 stainless steel.

[0016] (2) The present invention provides a low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel. Through environmental optimization, the laser welding penetration ability is significantly improved. Compared with conventional laser welding performed in an atmospheric environment, the welding heat input required to achieve the same penetration depth is lower, thereby reducing welding stress and suppressing the generation of welding cracks.

[0017] (3) The present invention provides a low vacuum laser welding method applicable to GH4169 high temperature alloy and SS304 stainless steel. By welding in a vacuum environment, the penetration ability and forming quality of laser welding are improved. Compared with electron beam welding, which requires a high vacuum environment, low vacuum laser welding can achieve significant benefits in a low vacuum environment of less than 10 kPa. The vacuuming time is short, the vacuum equipment cost is low, and the welding production efficiency is high.

[0018] (4) The present invention provides a low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel. Laser welding is performed in a low-vacuum environment, and the flow pattern of the laser welding molten pool changes. This flow pattern is less likely to generate eddy zones, and bubbles are more likely to escape, which can effectively suppress the generation of welding porosity defects.

[0019] (5) The low-vacuum laser welding method of the present invention applicable to GH4169 high-temperature alloy and SS304 stainless steel can obtain a weld with a large depth-to-width ratio and a low welding heat input required to form the same penetration depth, thus the cooling rate is fast. Since Nb elements continuously segregate from the dendrite interior to the grain boundary during the weld solidification process, forming a brittle Laves phase rich in Nb elements, increasing the cooling rate can reduce the weld solidification time, thereby suppressing Nb element segregation and effectively forming a brittle Laves phase in the weld.

[0020] (6) A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to the present invention controls the element content of dissimilar metal welds by adjusting the laser beam offset. When the laser beam is offset towards the GH4169 high-temperature alloy, the content of solid solution strengthening elements such as Mo and Nb and age-hardening elements such as Al and Ti inside the weld can be increased, thereby improving the solid solution strengthening and precipitation strengthening effects of the weld. When the laser beam is offset towards the SS304 stainless steel, the content of Nb inside the weld can be reduced, thereby inhibiting the formation of brittle Laves phase in the dissimilar metal weld from a metallurgical perspective. However, due to the low content of solid solution strengthening elements and age-hardening elements, it is not possible to achieve a significant increase in weld strength.

[0021] (7) After heat treatment, GH4169 alloy precipitates the strengthening phase γ'' (Ni3Nb) in the dissimilar metal weld, which greatly improves the strength of the dissimilar metal weld and thus obtains excellent high-temperature service performance.

[0022] The above comparison shows that the low-vacuum laser welding method of the present invention, applicable to GH4169 high-temperature alloy and SS304 stainless steel, can solve the problems of poor weld formation quality, shallow weld penetration, weld porosity and large precipitation of brittle phases inside the weld in traditional laser welding of GH4169 high-temperature alloy and SS304 plates. In addition, it can also increase the content of strengthening elements in dissimilar metal welds and improve weld strength.

[0023] This invention relates to a low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the welding system used in the low-vacuum laser welding of GH4169 high-temperature alloy and SS304 stainless steel in Example 1. 1 is the laser, 2 is the optical fiber, 3 is the laser head, 4 is the vacuum chamber, 5 is the weld seam, 6 is the observation window, 7 is the dissimilar metal sample to be welded, 8 is the moving platform, 9 is the welding worktable, 10 is the Roots pump, and 11 is the mechanical pump.

[0025] Figure 2 This is a schematic diagram of the joint type of the low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to the present invention. 12 is SS304 stainless steel and 13 is GH4169 high-temperature alloy.

[0026] Figure 3 This is a schematic diagram of the weld seam in the low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel in Example 1. 14 is the lock bottom depth, 15 is the lock bottom width, and 16 is the width of the parallel section.

[0027] Figure 4The images show the surface and cross-section of the weld seam of the untreated GH4169 high-temperature alloy / SS304 stainless steel weldment prepared in step two of Example 1. a is the surface forming, b is the cross-sectional forming, and c is the longitudinal section forming.

[0028] Figure 5 To compare the surface and cross-section of the weld of the untreated GH4169 high-temperature alloy / SS304 stainless steel weldment prepared in step two of Experiment 2, a is the surface forming, b is the cross-sectional forming, and c is the longitudinal section forming.

[0029] Figure 6 The images show a comparison of the weld cross-section formation and microstructure of the untreated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in Step 2 of Example 1 and Comparative Experiment 1. (a) shows the cross-section formation when the offset is -0.4 mm, (b) shows the cross-section formation when the offset is 0 mm, (c) shows the microstructure when the offset is -0.4 mm, and (d) shows the microstructure when the offset is 0 mm.

[0030] Figure 7 Comparison of weld metal element content of unheat-treated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in step two of Example 1 and Example 2;

[0031] Figure 8 The images show the low-magnification microstructure of the weld seam of the heat-treated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in step three under different beam offsets in Examples 1 to 4. (a) is 0 mm, (b) is 0.2 mm, (c) is 0.4 mm, and (d) is 0.6 mm.

[0032] Figure 9 The images show high-magnification microstructures of the weld seams of the heat-treated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in step three under different beam offsets in Examples 1 to 4. In the images, (a) is 0 mm, (b) is the high-magnification SEM structure corresponding to the marked area in (a), (c) is 0.2 mm, (d) is the high-magnification SEM structure corresponding to the marked area in (c), (e) is 0.4 mm, and (f) is 0.6 mm. Detailed Implementation

[0033] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0034] Specific Implementation Method 1: This implementation method describes a low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel, which is carried out according to the following steps:

[0035] I. Assembly of welded parts:

[0036] The dissimilar metal base materials to be welded are assembled and then fixed on a two-dimensional moving platform inside the vacuum chamber to form a dissimilar metal sample to be welded.

[0037] The dissimilar metal base materials to be welded are GH4169 high-temperature alloy and SS304 stainless steel;

[0038] II. Low-vacuum laser welding:

[0039] Under the conditions of laser power of 2kW~8kW, welding speed of 0.5mm / min~3.5mm / min, laser spot diameter of 0.4mm~0.6mm, laser beam incident angle of 80°~100°, laser defocusing amount of -3mm~-12mm, and laser beam offset of 0mm~0.6mm, a two-dimensional moving platform is moved, and the laser moves along the welding path to form a weld. After the laser welding is completed, the workpiece is cooled to room temperature and then removed.

[0040] III. Heat Treatment:

[0041] The weldment is subjected to a two-stage aging heat treatment, which completes the low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel.

[0042] In this specific embodiment, the selection of low-vacuum laser welding parameters is related to the type of dissimilar metal joint and the thickness of the base material. For example, for welding dissimilar metal base materials with a medium or greater thickness, a larger negative defocusing amount should be selected to set the laser focus position below the surface of the dissimilar metal joint to be welded, thereby enhancing the penetration capability of laser welding.

[0043] In this specific embodiment, the element content of dissimilar metal welds can be controlled by adjusting the laser beam offset. When the laser beam is offset towards the GH4169 high-temperature alloy, the content of solid solution strengthening elements such as Mo and Nb, and age-hardening elements such as Al and Ti, can be increased, thus improving the strengthening effect. Simultaneously, due to the rapid cooling rate of laser welding, the weld solidification time can be reduced, thereby suppressing Nb segregation and effectively preventing the formation of brittle Laves phases in the weld. When the laser beam is offset towards the SS304 stainless steel, although the Nb content inside the weld can be reduced, suppressing the formation of brittle Laves phases in the dissimilar metal weld from a metallurgical perspective, the lower content of solid solution strengthening elements and age-hardening elements prevents a significant increase in weld strength.

[0044] The beneficial effects of this embodiment are:

[0045] (1) A low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel in this embodiment is to perform laser welding in a low-vacuum environment through environmental optimization. Without increasing the welding heat input, it can effectively improve the welding penetration ability and weld formation quality, and obtain a high-quality weld with a large depth-to-width ratio for the dissimilar metal butt structure of GH4169 high-temperature alloy and SS304 stainless steel.

[0046] (2) The low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel in this embodiment significantly improves the penetration ability of laser welding through environmental optimization. Compared with conventional laser welding in atmospheric environment, the welding heat input required to achieve the same penetration depth is lower, thereby reducing welding stress and suppressing the generation of welding cracks.

[0047] (3) A low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel in this embodiment improves the penetration ability and forming quality of laser welding by welding in a vacuum environment. Compared with electron beam welding which requires a high vacuum environment, low-vacuum laser welding can achieve significant benefits in a low vacuum environment of less than 10 kPa. The vacuuming time is short, the vacuum equipment cost is low, and the welding production efficiency is high.

[0048] (4) A low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel in this embodiment is to perform laser welding in a low-vacuum environment. The flow pattern of the laser welding molten pool changes. This flow pattern is less likely to generate eddy zones and bubbles are more likely to escape, which can effectively suppress the generation of welding porosity defects.

[0049] (5) The low-vacuum laser welding method of this embodiment, applicable to GH4169 high-temperature alloy and SS304 stainless steel, can obtain a weld with a large depth-to-width ratio and a low welding heat input required to form the same penetration depth, thus resulting in a fast cooling rate. Since Nb elements continuously segregate from the dendrite interior to the grain boundary during the weld solidification process, forming a brittle Laves phase rich in Nb elements, increasing the cooling rate can reduce the weld solidification time, thereby suppressing Nb element segregation and effectively forming a brittle Laves phase in the weld.

[0050] (6) A low-vacuum laser welding method applicable to GH4169 high-temperature alloy and SS304 stainless steel in this embodiment controls the element content of dissimilar metal welds by adjusting the laser beam offset. When the laser beam is offset towards the GH4169 high-temperature alloy, the content of solid solution strengthening elements such as Mo and Nb and age-hardening elements such as Al and Ti inside the weld can be increased, thereby improving the solid solution strengthening and precipitation strengthening effects of the weld. When the laser beam is offset towards the SS304 stainless steel, the content of Nb inside the weld can be reduced, thereby inhibiting the formation of brittle Laves phase in the dissimilar metal weld from a metallurgical perspective. However, due to the low content of solid solution strengthening elements and age-hardening elements, it is not possible to achieve a significant increase in weld strength.

[0051] (7) After heat treatment, GH4169 alloy precipitates the strengthening phase γ'' (Ni3Nb) in the dissimilar metal weld, which greatly improves the strength of the dissimilar metal weld and thus obtains excellent high-temperature service performance.

[0052] The above comparison shows that the low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel in this embodiment can solve the problems of poor weld formation quality, shallow weld penetration, weld porosity and large precipitation of brittle phases inside the weld in traditional laser welding of GH4169 high-temperature alloy and SS304 plates. In addition, it can also increase the content of strengthening elements in dissimilar metal welds and improve weld strength.

[0053] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the dissimilar metal base materials to be welded in step one are pre-treated dissimilar metal base materials to be welded; the pre-treatment involves mechanically grinding the mating surfaces and surfaces of the dissimilar metal base materials to be welded using a polishing machine, and then wiping them with anhydrous ethanol or acetone. Everything else is the same as in Specific Implementation Method One.

[0054] In this specific embodiment, mechanical grinding and cleaning are performed to remove oil and oxide film from the dissimilar metal plates to be welded and the mating surfaces.

[0055] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: in step one, the dissimilar metal base materials to be welded are assembled to form a butt joint or a lock-bottom butt joint. Everything else is the same as in Specific Implementation Method One or Two.

[0056] Specific implementation method four: Combination Figure 2 Specifically, this embodiment differs from one of embodiments one to three in that, when assembling the dissimilar metal base materials to be welded to form a butt joint, the thickness of the dissimilar metal base materials to be welded is 2mm to 20mm. Everything else is the same as in embodiments one to three.

[0057] Specific Implementation Method Five: Combining Figure 2 Specifically, this embodiment differs from one of embodiments one to four in that: when assembling the dissimilar metal base materials to be welded to form a lock-bottom butt joint, the lock-bottom width is 1mm to 10mm, and the lock-bottom depth is 1mm to 19mm. Everything else is the same as in embodiments one to four.

[0058] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step one, the dissimilar metal base materials to be welded are assembled, with an assembly gap of 0mm to 0.2mm. Everything else is the same as in Specific Implementation Methods One to Five.

[0059] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that the environmental pressure for laser welding in step two is 10... -2 kPa~1kPa. Other aspects are the same as in any of the specific implementation methods one to six.

[0060] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the laser welding environment in step two is an argon atmosphere or an air atmosphere. Everything else is the same as in Specific Implementation Methods One to Seven.

[0061] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that: in step two, the laser beam offset is the horizontal distance of the laser spot center from the docking surface. Offset towards the GH4169 high-temperature alloy side is considered positive, and offset towards the SS304 stainless steel side is considered negative. Everything else is the same as in Specific Implementation Methods One through Eight.

[0062] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the two-stage aging heat treatment described in step two involves holding the weldment at 720°C for 8 hours, then cooling it to 620°C at a controlled cooling rate of 50°C / h, holding it at 620°C for 8 hours, and finally air-cooling it to room temperature. Everything else is the same as in Specific Implementation Methods One to Nine.

[0063] The beneficial effects of the present invention are verified using the following embodiments:

[0064] Example 1, combined with Figure 1 and 3 Detailed explanation:

[0065] A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel is performed according to the following steps:

[0066] I. Assembly of welded parts:

[0067] The dissimilar metal base materials to be welded are assembled and then fixed on a two-dimensional moving platform inside the vacuum chamber to form a dissimilar metal sample to be welded.

[0068] The dissimilar metal base materials to be welded are GH4169 high-temperature alloy and SS304 stainless steel;

[0069] II. Low-vacuum laser welding:

[0070] Under the conditions of an ambient pressure of 1 kPa, an argon atmosphere, a laser power of 4 kW, a welding speed of 0.6 mm / min, a laser spot diameter of 0.4 mm, a laser beam incident angle of 90°, a laser defocusing amount of -6 mm, and a laser beam offset of 0 mm, a two-dimensional moving platform is moved, and the laser moves along the welding path to form a weld. After the laser welding is completed and cooled to room temperature, the air inlet valve is opened, air enters the vacuum chamber, and the welded part is taken out, which is the untreated GH4169 high-temperature alloy / SS304 stainless steel welded part.

[0071] III. Heat Treatment:

[0072] The weldment was held at 720℃ for 8 hours, then cooled to 620℃ at a controlled cooling rate of 50℃ / h, and held at 620℃ for 8 hours. Finally, it was air-cooled to room temperature to obtain the heat-treated GH4169 high-temperature alloy / SS304 stainless steel weldment.

[0073] The dissimilar metal base material to be welded mentioned in step one is the pre-treated dissimilar metal base material to be welded; the pre-treatment involves mechanically grinding the mating surfaces and surfaces of the dissimilar metal base materials to be welded using a polishing machine, and then wiping them with industrial silk soaked in anhydrous ethanol.

[0074] In step one, the dissimilar metal base materials to be welded are assembled to form a lock-bottom butt joint; the thickness of the dissimilar metal base materials to be welded is 10mm.

[0075] When assembling dissimilar metal base materials to be welded into a lock-bottom butt joint, the lock bottom width is 4mm and the lock bottom depth is 6mm.

[0076] In step one, the dissimilar metal base materials to be welded are assembled with an assembly gap of 0mm.

[0077] In step two, the laser beam offset is the horizontal distance of the laser spot center from the docking surface. We assume that the offset towards the GH4169 high-temperature alloy side is positive and the offset towards the SS304 stainless steel side is negative.

[0078] In step two, the laser beam offset is 0mm, meaning the laser beam is aligned with the mating surfaces of the dissimilar metal base materials.

[0079] Figure 1This is a schematic diagram of the welding system used in Example 1 for low-vacuum laser welding of GH4169 high-temperature alloy and SS304 stainless steel. 1 is the laser, 2 is the optical fiber, 3 is the laser head, 4 is the vacuum chamber, 5 is the weld seam, 6 is the observation window, 7 is the dissimilar metal sample to be welded, 8 is the moving platform, 9 is the welding worktable, 10 is the Roots pump, and 11 is the mechanical pump. The laser is a high-power fiber laser with a rated power of 10kW. The vacuum system consists of a Roots pump and a mechanical pump. During the vacuuming process, the mechanical pump reduces the ambient pressure to below 15kPa, then the Roots pump opens to continue reducing the ambient pressure to the set value. During welding, the sample to be welded is fixed to the two-dimensional moving platform using a clamp. The laser head position is fixed during welding, and the welding direction and speed are controlled by the two-dimensional moving platform. The laser and vacuum chamber are connected by an optical fiber; the optical fiber used in Example 1 has a diameter of 200μm. The vacuum system and vacuum chamber are connected by pipes.

[0080] Example 2: This example differs from Example 1 in that the laser beam offset in step 2 is 0.4mm, meaning the laser beam is offset 0.4mm towards the GH4169 high-temperature alloy side. Everything else is the same as in Example 1.

[0081] Example 3: This example differs from Example 1 in that the laser beam offset in step 2 is 0.2mm, meaning the laser beam is offset 0.2mm towards the GH4169 high-temperature alloy side. Everything else is the same as in Example 1.

[0082] Example 4: This example differs from Example 1 in that the laser beam offset in step 2 is 0.6mm, meaning the laser beam is offset 0.6mm towards the GH4169 high-temperature alloy side. Everything else is the same as in Example 1.

[0083] Comparative Experiment 1: The difference between this embodiment and Embodiment 1 is that the laser beam offset in step 2 is -0.4mm, that is, the laser beam is offset 0.4mm towards the SS304 stainless steel side. Everything else is the same as in Embodiment 1.

[0084] Comparative Experiment 2: This example differs from Example 1 in that the environmental pressure in step 2 is atmospheric pressure, i.e., 101 kPa. Everything else is the same as in Example 1.

[0085] Figure 4The figures show the surface and cross-section of the weld seam of the untreated GH4169 high-temperature alloy / SS304 stainless steel weldment prepared in step two of Example 1. a) shows the surface formation, b) shows the cross-sectional formation, and c) shows the longitudinal section formation. As shown, low-vacuum laser welding of the dissimilar metals GH4169 high-temperature alloy and SS304 stainless steel was performed at an ambient pressure of 1 kPa. The weld seam surface exhibited a silvery-white metallic luster, with very uniform longitudinal formation and clean, regular transverse formation. There were no welding defects such as undercut or spatter. The weld cross-section showed high penetration depth and a large depth-to-width ratio, and was free of defects such as porosity and cracks. The weld penetration depth was 8.02 mm, the average penetration width of the parallel section was 1.53 mm, and the weld depth-to-width ratio was 5.24.

[0086] Figure 5 To compare the surface and cross-section of the untreated GH4169 high-temperature alloy / SS304 stainless steel weldment prepared in step two of Experiment 2, a shows the surface formation, b shows the cross-sectional formation, and c shows the longitudinal section formation. As shown in the figure, compared with Example 1, the surface formation of the GH4169 high-temperature alloy and SS304 stainless steel dissimilar metal laser welding performed in an atmospheric environment is extremely uneven, with noticeable undercut and severe weld spatter defects. The weld penetration is significantly shallower, and weld porosity defects appear, resulting in a significant reduction in the overall quality. The weld penetration is 4.51 mm, the average weld width in parallel sections is 2.14 mm, and the weld depth-to-width ratio is 2.10.

[0087] Figure 6The figures show a comparison of the weld cross-section formation and microstructure of the untreated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in Example 1 and Comparative Experiment 1, Step 2. (a) shows the cross-section formation with an offset of -0.4 mm, (b) shows the cross-section formation with an offset of 0 mm, (c) shows the microstructure with an offset of -0.4 mm, and (d) shows the microstructure with an offset of 0 mm. As shown in the figures, (a) and (b) show that when the laser beam is offset towards the stainless steel base material, the weld penetration and geometry do not change significantly, there are no welding defects, and the forming quality is excellent. (c) and (d) show that when the laser beam is offset towards the stainless steel base material, the content of the brittle Laves phase in the weld is significantly reduced, with the volume fraction decreasing from 4.4% to 2.36%. This is because SS304 stainless steel does not contain Nb, which forms the Laves phase. By adjusting the laser beam offset, the content of alloying elements in the dissimilar metal weld can be adjusted, thus suppressing the formation of the brittle phase. The weld penetration depth of the GH4169 high-temperature alloy / SS304 stainless steel weldment prepared in Comparative Experiment 1 was 7.65 mm, the average weld width in parallel sections was 1.63 mm, the weld depth-to-width ratio was 4.69, and the volume fraction of Laves phase in the weld was 2.36%. The weld penetration depth of the GH4169 high-temperature alloy / SS304 stainless steel weldment prepared in Example 1 was 8.02 mm, the average weld width in parallel sections was 1.53 mm, the weld depth-to-width ratio was 5.24, and the volume fraction of Laves phase in the weld was 4.44%.

[0088] Using ImageJ image analysis software, the weld penetration depth of the untreated GH4169 high-temperature alloy / SS304 stainless steel weldment prepared in step two of Example 2 was 7.52 mm, the average weld width of the parallel section was 1.57 mm, the weld depth-to-width ratio was 4.79, and the volume fraction of Laves phase was 5.28%.

[0089] Figure 7Comparison of weld metal element content of untreated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in step two of Examples 1 and 2. As shown in the figure, when the offset is 0 mm, the mass fraction of Nb in the weld is 4.44%, Mo is 2.04%, Al is 0.33%, and Ti is 0.60%. Simultaneously, the mass fraction of Ni is 31.42% and Cr is 19.02%. When the offset is 0.4 mm, the mass fraction of Nb in the weld is 5.28%, Mo is 2.39%, Al is 0.39%, and Ti is 0.76%. Simultaneously, the mass fraction of Ni is 34.81% and Cr is 18.75%. This means that when the laser beam is offset towards the high-temperature alloy base material, the content of solid solution strengthening elements such as Mo and age-hardening elements such as Al and Ti in the weld increases accordingly, enhancing both the solid solution strengthening effect and the second-phase precipitation strengthening effect in the weld. This improves the mechanical properties of the dissimilar metal joint. According to the GB / T228 standard test, the tensile strength increases from 728.6 MPa corresponding to a beam offset of 0 mm to 777.5 MPa corresponding to a beam offset of 0.4 mm.

[0090] Tests showed that the element content of the weld metal of the untreated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in step two of the first comparative experiment was reduced, resulting in a decrease in the tensile strength of the weld to 690.1 MPa. The weld joint in the second comparative experiment was not fully penetrated, so no tensile strength test was performed.

[0091] Figure 8 The images show the low-magnification microstructure of the weld seams of the heat-treated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in step three under different beam offsets in Examples 1 to 4. (a) is 0 mm, (b) is 0.2 mm, (c) is 0.4 mm, and (d) is 0.6 mm. ImageJ image analysis software analysis showed that the volume fraction of the Laves phase in Figure (a) was 4.44%, in Figure (b) it was 4.96%, in Figure (c) it was 5.28%, and in Figure (d) it was 5.57%. It can be seen from the figures that the volume fraction of the white Laves phase in the weld seam increases with the increase of beam offset. This is related to the increase in Nb content in the weld seam due to the increase in offset. However, because the content of solid solution strengthening elements such as Mo and Nb and age-hardening elements such as Al and Ti is increased inside the weld seam, it still exhibits excellent weld strength.

[0092] Figure 9The images show high-magnification SEM images of the weld seams of the heat-treated GH4169 high-temperature alloy / SS304 stainless steel welded parts prepared in step three of Examples 1 to 4 under different beam offsets. (a) is 0 mm, (b) is the high-magnification SEM structure corresponding to the marked area in (a), (c) is 0.2 mm, (d) is the high-magnification SEM structure corresponding to the marked area in (c), (e) is 0.4 mm, and (f) is 0.6 mm. As can be seen from the images, the content of strengthening elements in the weld seam continuously increases, resulting in a continuous increase in the content of fine-sized white γ” phases. These phases, which were initially dispersed in (a) and (c), are transformed into a large-area concentrated distribution as seen in (e) and (f), significantly enhancing the precipitation strengthening effect of the weld seam. Therefore, as the laser beam deflects towards the GH4169 high-temperature alloy, the weld strength initially increases gradually. Simultaneously, due to the increased Nb content in the weld, the content of the brittle Laves phase also increases accordingly. Thus, when the beam deflection increases to 0.6 mm, the tensile strength of the weld decreases. At a deflection of 0 mm, the weld tensile strength is 792.3 MPa, and the weld joint fractures at the weld; at a deflection of 0.2 mm, the weld tensile strength is 814.9 MPa, and the weld joint fractures at the weld; at a deflection of 0.4 mm, the weld tensile strength is 838.0 MPa, and the weld joint fractures at the SS304 base material; at a deflection of 0.6 mm, the weld tensile strength is 819.5 MPa, and the weld joint fractures at the weld.

Claims

1. A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel, characterized in that... It is done in the following steps: I. Assembly of welded parts: The dissimilar metal base materials to be welded are assembled and then fixed on a two-dimensional moving platform inside the vacuum chamber to form a dissimilar metal sample to be welded. The dissimilar metal base materials to be welded are GH4169 high-temperature alloy and SS304 stainless steel; II. Low-vacuum laser welding: Under the conditions of laser power of 2kW~8kW, welding speed of 0.5mm / min~3.5mm / min, laser spot diameter of 0.4mm~0.6mm, laser beam incident angle of 80°~100°, laser defocusing amount of -3mm~-12mm, and laser beam offset of 0mm~0.6mm, a two-dimensional moving platform is moved, and the laser moves along the welding path to form a weld. After the laser welding is completed, the workpiece is cooled to room temperature and then removed. The ambient pressure for laser welding in step two is 10. -2 kPa~1kPa; In step two, the laser beam offset is the horizontal distance of the laser spot center from the docking surface. We assume that the offset towards the GH4169 high-temperature alloy side is positive and the offset towards the SS304 stainless steel side is negative. III. Heat Treatment: The weldment is subjected to a two-stage aging heat treatment, which completes the low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel.

2. The low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to claim 1, characterized in that... The dissimilar metal base material to be welded mentioned in step one is the pre-treated dissimilar metal base material to be welded; the pre-treatment involves mechanically grinding the mating surfaces and surfaces of the dissimilar metal base materials to be welded using a polishing machine, and then wiping them with anhydrous ethanol or acetone.

3. The low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to claim 1, characterized in that... In step one, the dissimilar metal base materials to be welded are assembled to form a butt joint or a lock-bottom butt joint.

4. A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to claim 3, characterized in that... When dissimilar metal base materials to be welded are assembled to form a butt joint, the thickness of the dissimilar metal base materials to be welded is 2mm~20mm.

5. A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to claim 3, characterized in that... When dissimilar metal base materials to be welded are assembled to form a lock-bottom butt joint, the lock bottom width is 1mm~10mm and the lock bottom depth is 1mm~19mm.

6. A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to claim 1, characterized in that... In step one, the dissimilar metal base materials to be welded are assembled, with an assembly gap of 0mm~0.2mm.

7. A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to claim 1, characterized in that... In step two, the laser welding environment is either argon or air.

8. A low-vacuum laser welding method for GH4169 high-temperature alloy and SS304 stainless steel according to claim 1, characterized in that... The two-stage aging heat treatment described in step three involves holding the weldment at 720°C for 8 hours, then cooling it to 620°C at a controlled cooling rate of 50°C / h, holding it at 620°C for 8 hours, and finally air-cooling it to room temperature.

Images